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00146caa | 1 | /* $OpenBSD: ssh-dss.c,v 1.22 2006/07/22 20:48:23 stevesk Exp $ */ |
4f8c6159 | 2 | /* |
3 | * Copyright (c) 2000 Markus Friedl. All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms, with or without | |
6 | * modification, are permitted provided that the following conditions | |
7 | * are met: | |
8 | * 1. Redistributions of source code must retain the above copyright | |
9 | * notice, this list of conditions and the following disclaimer. | |
10 | * 2. Redistributions in binary form must reproduce the above copyright | |
11 | * notice, this list of conditions and the following disclaimer in the | |
12 | * documentation and/or other materials provided with the distribution. | |
4f8c6159 | 13 | * |
14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
15 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
16 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
17 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
18 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
19 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
20 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
21 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
23 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
24 | */ | |
25 | ||
26 | #include "includes.h" | |
42f11eb2 | 27 | |
28 | #include <openssl/bn.h> | |
29 | #include <openssl/evp.h> | |
4f8c6159 | 30 | |
00146caa | 31 | #include <string.h> |
32 | ||
4f8c6159 | 33 | #include "xmalloc.h" |
34 | #include "buffer.h" | |
35 | #include "bufaux.h" | |
36 | #include "compat.h" | |
42f11eb2 | 37 | #include "log.h" |
4f8c6159 | 38 | #include "key.h" |
39 | ||
40 | #define INTBLOB_LEN 20 | |
41 | #define SIGBLOB_LEN (2*INTBLOB_LEN) | |
42 | ||
4f8c6159 | 43 | int |
b6c7b7b7 | 44 | ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, |
45 | const u_char *data, u_int datalen) | |
4f8c6159 | 46 | { |
4f8c6159 | 47 | DSA_SIG *sig; |
714954dc | 48 | const EVP_MD *evp_md = EVP_sha1(); |
4f8c6159 | 49 | EVP_MD_CTX md; |
eb9f2fab | 50 | u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; |
d87596b0 | 51 | u_int rlen, slen, len, dlen; |
4f8c6159 | 52 | Buffer b; |
53 | ||
54 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 55 | error("ssh_dss_sign: no DSA key"); |
4f8c6159 | 56 | return -1; |
57 | } | |
4f8c6159 | 58 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 59 | EVP_DigestUpdate(&md, data, datalen); |
087dea86 | 60 | EVP_DigestFinal(&md, digest, &dlen); |
4f8c6159 | 61 | |
42f11eb2 | 62 | sig = DSA_do_sign(digest, dlen, key->dsa); |
087dea86 | 63 | memset(digest, 'd', sizeof(digest)); |
d87596b0 | 64 | |
d87596b0 | 65 | if (sig == NULL) { |
66 | error("ssh_dss_sign: sign failed"); | |
67 | return -1; | |
68 | } | |
4f8c6159 | 69 | |
70 | rlen = BN_num_bytes(sig->r); | |
71 | slen = BN_num_bytes(sig->s); | |
72 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { | |
d6133f43 | 73 | error("bad sig size %u %u", rlen, slen); |
4f8c6159 | 74 | DSA_SIG_free(sig); |
75 | return -1; | |
76 | } | |
4f8c6159 | 77 | memset(sigblob, 0, SIGBLOB_LEN); |
78 | BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); | |
79 | BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); | |
80 | DSA_SIG_free(sig); | |
81 | ||
d0c832f3 | 82 | if (datafellows & SSH_BUG_SIGBLOB) { |
4f8c6159 | 83 | if (lenp != NULL) |
84 | *lenp = SIGBLOB_LEN; | |
eb9f2fab | 85 | if (sigp != NULL) { |
86 | *sigp = xmalloc(SIGBLOB_LEN); | |
87 | memcpy(*sigp, sigblob, SIGBLOB_LEN); | |
88 | } | |
4f8c6159 | 89 | } else { |
90 | /* ietf-drafts */ | |
91 | buffer_init(&b); | |
fa08c86b | 92 | buffer_put_cstring(&b, "ssh-dss"); |
4f8c6159 | 93 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); |
94 | len = buffer_len(&b); | |
4f8c6159 | 95 | if (lenp != NULL) |
96 | *lenp = len; | |
eb9f2fab | 97 | if (sigp != NULL) { |
98 | *sigp = xmalloc(len); | |
99 | memcpy(*sigp, buffer_ptr(&b), len); | |
100 | } | |
101 | buffer_free(&b); | |
4f8c6159 | 102 | } |
103 | return 0; | |
104 | } | |
105 | int | |
b6c7b7b7 | 106 | ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, |
107 | const u_char *data, u_int datalen) | |
4f8c6159 | 108 | { |
4f8c6159 | 109 | DSA_SIG *sig; |
714954dc | 110 | const EVP_MD *evp_md = EVP_sha1(); |
4f8c6159 | 111 | EVP_MD_CTX md; |
087dea86 | 112 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
1e3b8b07 | 113 | u_int len, dlen; |
d87596b0 | 114 | int rlen, ret; |
115 | Buffer b; | |
4f8c6159 | 116 | |
117 | if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { | |
fa08c86b | 118 | error("ssh_dss_verify: no DSA key"); |
4f8c6159 | 119 | return -1; |
120 | } | |
121 | ||
4f8c6159 | 122 | /* fetch signature */ |
d0c832f3 | 123 | if (datafellows & SSH_BUG_SIGBLOB) { |
b6c7b7b7 | 124 | sigblob = xmalloc(signaturelen); |
125 | memcpy(sigblob, signature, signaturelen); | |
4f8c6159 | 126 | len = signaturelen; |
127 | } else { | |
128 | /* ietf-drafts */ | |
74fc9186 | 129 | char *ktype; |
4f8c6159 | 130 | buffer_init(&b); |
cf54363d | 131 | buffer_append(&b, signature, signaturelen); |
4f8c6159 | 132 | ktype = buffer_get_string(&b, NULL); |
fa08c86b | 133 | if (strcmp("ssh-dss", ktype) != 0) { |
134 | error("ssh_dss_verify: cannot handle type %s", ktype); | |
74fc9186 | 135 | buffer_free(&b); |
abc4e9a7 | 136 | xfree(ktype); |
74fc9186 | 137 | return -1; |
138 | } | |
abc4e9a7 | 139 | xfree(ktype); |
cf54363d | 140 | sigblob = buffer_get_string(&b, &len); |
4f8c6159 | 141 | rlen = buffer_len(&b); |
abc4e9a7 | 142 | buffer_free(&b); |
6aacefa7 | 143 | if (rlen != 0) { |
abc4e9a7 | 144 | error("ssh_dss_verify: " |
145 | "remaining bytes in signature %d", rlen); | |
146 | xfree(sigblob); | |
74fc9186 | 147 | return -1; |
148 | } | |
4f8c6159 | 149 | } |
150 | ||
151 | if (len != SIGBLOB_LEN) { | |
d6133f43 | 152 | fatal("bad sigbloblen %u != SIGBLOB_LEN", len); |
4f8c6159 | 153 | } |
154 | ||
155 | /* parse signature */ | |
b775c6f2 | 156 | if ((sig = DSA_SIG_new()) == NULL) |
157 | fatal("ssh_dss_verify: DSA_SIG_new failed"); | |
158 | if ((sig->r = BN_new()) == NULL) | |
159 | fatal("ssh_dss_verify: BN_new failed"); | |
160 | if ((sig->s = BN_new()) == NULL) | |
161 | fatal("ssh_dss_verify: BN_new failed"); | |
4f8c6159 | 162 | BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); |
163 | BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); | |
d0c832f3 | 164 | |
b6c7b7b7 | 165 | /* clean up */ |
166 | memset(sigblob, 0, len); | |
167 | xfree(sigblob); | |
2b87da3b | 168 | |
a306f2dd | 169 | /* sha1 the data */ |
4f8c6159 | 170 | EVP_DigestInit(&md, evp_md); |
a306f2dd | 171 | EVP_DigestUpdate(&md, data, datalen); |
087dea86 | 172 | EVP_DigestFinal(&md, digest, &dlen); |
4f8c6159 | 173 | |
fa08c86b | 174 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); |
087dea86 | 175 | memset(digest, 'd', sizeof(digest)); |
4f8c6159 | 176 | |
4f8c6159 | 177 | DSA_SIG_free(sig); |
178 | ||
d87596b0 | 179 | debug("ssh_dss_verify: signature %s", |
180 | ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); | |
4f8c6159 | 181 | return ret; |
182 | } |